1. Field of the Invention
This invention relates to expansion joints and particularly to expansion joints for coke ovens. More particularly, the invention concerns a new offset expansion joint for installation in the brickwork in the area of the horizontal flue during repair or rehabilitation of coke ovens, especially those designed by Koppers, Carl Still, Otto, Wilputte, Didier and Nippon Steel. The invention also relates to the method of installing the offset expansion joint.
2. Brief Description of the Prior Art
Until about 1970, most coke oven batteries in the United States were 4 meter batteries which were built for an expected life of about 20 years. In the 1970's the industry began to install batteries which were greater than 5 meters, and usually were 6 meters, which have about an 8-10 year life span based upon industry experience, at which time they must be repaired or rehabilitated.
It was expected that the techniques previously used to repair prior 4 meter batteries, namely rebuilding of the oven walls using various types of compressible material disposed in horizontal cross-section in the brickwork, could be applied to the 6 meter batteries. However, these techniques have not been completely successful.
As is well known, it is important to prohibit the leakage of raw coke oven gas from the oven chambers through the oven brickwork into the flue chambers. Such flue gas leakage is generally attributed to excessive spacing or gaps between bricks. The main reason for flue gas leakage occurs at the interface between old brickwork and new brickwork.
Leakage of coke oven gas into the flues may result in ignition, causing temperatures in excess of oven design which would destroy the silica brick. In addition, if the gases do not ignite totally within the flue system, but are evacuated to atmosphere through the waste heat stack, such gases may result in violation of government standards, such as the Environmental Protection Act, which may require the installation of expensive electrostatic precipitators in the waste heat system.
Due to the unpredictability of the expansion of the old brick and the new brick used in rebuilding the larger size coke ovens, the compressible materials installed using prior techniques are insufficient to prevent leakage of the coke oven gases. In the past, expansion joints of various materials, such as wood, spun silica, compressible mortar or the like have been used between bricks in adjacent tiers of a coke oven, but never in an offset relationship. It has now been recognized by the inventor that a new type expansion joint was needed to compensate for the unpredictable expansion of new brick when heated.